SECTION III., 1895. [97 | Trans. R. S. C, 
VII.— Viscosity in Liquids, and Instruments for its Measurement. 
By ANTHONY McGitt, B.A., B.Sc., Assistant Analyst, Inland Revenue 
AE Department. 
Presented by Thomas Macfarlane, Esq., F.R.S.C., Chief Analyst, ete. 
(Read May, 1895.) 
This paper is, in large part, historical, and sketches the progress of 
viscosimetric work, giving some account of the nature of the results 
obtained, and the various forms of instruments which have been devised 
and employed. These latter are, for purposes of study, classified as 
follows : 
Class I.—Instruments designed for the determination of true viscosity, 
i.e., internal fluid friction. 
Class I1.—Instruments whose operation depends upon the surface tension 
and the density, rather than the true viscosity of the liquids 
examined. 
Class I1].—Efiiux instruments in which a constant head of pressure is 
maintained during flow. 
Class [V.—Eftlux instruments working under varying pressure. 
Class V.—Mechanical devices for testing the lubricating qualities of 
oils under conditions more or less similar to those obtaining 
. 
in actual use. 
Class VI.—Viscosity apparatus not belonging to any of the former classes. 
Under Class IV. the following record of work done with an instru- 
ment designed by the author of the paper occurs : 
A is a cylindrical vessel of brass, five 
inches in each dimension ; B isa re-entering 
cone, 14 inches high, 1 inch diam. below 
and + inch at top. Into this are fitted 
(by ground joints) the nozzles C, as shown 
enlarged in the lower figure. D is a strip 
of bent copper to serve asa gauge. The 
vertical distance between the points E and 
F is 24 inches. 
The brass vessel is cast in one piece 
and shaped on the lathe ; its walls are one- 
quarter of an inch thick. The large size 
of the cup enables it to contain 1,200 cc. 
of oil at the beginning of each test. The 
small portion (50 cc.) withdrawn flows at 
a practically uniform rate throughout the 
SECTE 1siys 7 

